This invention relates to a prober for testing electric characteristics of a cooled specimen or the like in a vacuum atmosphere and a low-temperature test equipment having such a prober incorporated therein, and more particularly to a prober suitable for use for a semiconductor wafer test equipment for testing a semiconductor wafer and a low-temperature test equipment having such a prober incorporated therein.
In recent years, it has been highly demanded that a semiconductor device is subjected to measurement of electric characteristics thereof or the like at an ultra-low temperature in a vacuum atmosphere for the purpose of ensuring reliable screening due to detection of an abnormal leakage current which fails to be detected in a room temperature, checking of operation of a low-temperature operation device such as a high-precision photo detector, a superconductive device or the like, measurement of physical characteristics of a device or pure wafer element at a low temperature by DLTS techniques or the like to measure various characteristics thereof such as a concentration of impurities therein, and the like.
For this purpose, a test equipment is proposed in the art which includes a vacuum chamber formed so as to be evacuated at a vacuum by means of a vacuum pump, a wafer holder arranged in the vacuum chamber, an ultra-low temperature refrigerator having a cooling head positioned in the vacuum chamber, and the like. Also, another test equipment is known in the art, as disclosed in Japanese Patent Application Laid-Open Publication No. 137547/1992. The test equipment includes a vacuum chamber, a spare chamber arranged adjacently to the vacuum chamber and configured so as to communicate through a gate valve with the vacuum chamber and temporarily store semiconductor wafers each of which is an object to be tested (tested object) therein. The test equipment is so constructed that the spare chamber is evacuated at a vacuum when the wafer is accessed to the vacuum chamber and the gate valve is closed to increase a pressure in only the spare chamber to an atmospheric level when the wafers each are removed from the spare chamber. This ensures that the vacuum chamber is constantly kept at a vacuum, to thereby successively subject the semiconductor wafers to a test under ultra-low temperature conditions.
The conventional test equipment described above generally has a prober which is constructed as shown in FIGS. 4 and 5 incorporated therein. More specifically, the prober generally designated at reference numeral 100 includes a probe card 101 constituted by a printed circuit board (PCB) formed into a substantially ring-like shape, a hole 101a defined by an inner peripheral edge of the probe card 101 and probe needles 102 arranged on the inner peripheral edge of the probe card 101 so as to inwardly extend therefrom or extend toward a center of the hole 101a. The probe needles 102, as shown in FIG. 5, each have a proximal end 102a fixedly supported on one surface of the probe card 101 by means of an adhesive and a distal end 102b arranged so as to extend toward the center of the hole 101a. Also, the prober 100 is securely arranged in a vacuum chamber (now shown) through an arm 103. The arm 103 may be supported so as to be longitudinally, laterally and/or vertically movable as required.
A specimen holder or semiconductor wafer holder 110 is controlled to permit the distal end 102b of each of the probe needles 102 to be contacted with an electrode of each of devices mounted on a specimen or semiconductor wafer supported on the semiconductor wafer holder 110, to thereby measure electric characteristics of the devices of the semiconductor wafer.
In order to more accurately measure electric characteristics of the devices mounted on the semiconductor wafer, it is desired to reduce transmission of heat from the prober 100 through the probe needles 102 to the devices as much as possible. Also, the probe needles 102 are mounted on the probe card 101 so as to be aligned with the electrodes of the devices on the semiconductor wafer. However, the low-temperature test causes heat shrinkage of the probe card 101, to thereby render positional registration or alignment of the probe needles 102 with the specimen difficult.
The present invention has been made in view of the foregoing disadvantage of the prior art.
Accordingly, it is an object of the present invention to provide a prober which is capable of reducing heat transmission from a probe card to a specimen to be tested (tested specimen) when it is subjected to a test under vacuum and low or ultra-low temperature conditions, to thereby enhance accuracy of the test.
It is another object of the present invention to provide a prober which is capable of absorbing thermal shrinkage of a probe card to facilitate positional registration or alignment between probe needles and a tested specimen while increasing accuracy of the alignment, to thereby further enhance accuracy of a test of the specimen.
It is a further object of the present invention to provide a prober which is capable of being suitable for a test of a semiconductor wafer.
It is still another object of the present invention to provide a low-temperature test equipment which is capable of reducing heat transmission from a prober to a tested specimen when it is subjected to a test under vacuum and low or ultra-low temperature conditions, to thereby enhance accuracy of the test.
It is yet another object of the present invention to provide a low-temperature test equipment which is capable of absorbing thermal shrinkage of a probe card to facilitate positional registration or alignment between probe needles and a tested specimen while increasing accuracy of the alignment, to thereby further enhance accuracy of a test for the specimen.
It is a still further object of the present invention to provide a low-temperature test equipment which is capable of being suitable for a test of a semiconductor wafer.
In accordance with one aspect of the present invention, a prober for a test of a specimen supported on a specimen holder cooled which is carried out in a vacuum chamber is provided. The prober includes a probe card formed into a substantially ring-like shape, at least one heat insulating member arranged on one surface of the probe card in a laminated manner or laminatedly so as to be positioned in proximity to an inner peripheral edge of the probe card, and probe needles each arranged in a manner to be contacted with the heat insulating member and having a distal end projected inwardly of the inner peripheral edge of the probe card.
In a preferred embodiment of the present invention, the heat insulating member is joined through an adhesive, such as an epoxy adhesive, to the one surface of the probe card.
In a preferred embodiment of the present invention, the thermal transfer regulating member is joined through an adhesive to the one surface of the probe card.
In a preferred embodiment of the present invention, a plurality of the heat insulating members are joined to each other by means of an adhesive, such as an epoxy adhesive, to thereby form a laminate.
In a preferred embodiment of the present invention, the heat insulating member is made of a ceramic material.
In a preferred embodiment of the present invention, the specimen is a semiconductor wafer and the specimen holder is a wafer holder, whereby the prober is used for a test of the semiconductor wafer supported on the wafer holder cooled which is carried out in the vacuum chamber.
In accordance with another aspect of the present invention, a low-temperature test equipment is provided. The low-temperature test equipment includes such a prober constructed as described above.
In a preferred embodiment of the low-temperature test equipment of the present invention, the specimen is a semiconductor wafer and the specimen holder is a wafer holder, whereby the prober is used for a test of the semiconductor wafer supported on the wafer holder cooled which is carried out in the vacuum chamber.